Feature suggestion: Add amplitude and phase results to the output of model tides, and add a parameter to indicate whether to output amplitude and phase results

[q1165600785]

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I now want to know the amplitude and phase obtained by interpolating different tidal models, rather than the final superimposed result of sea tide height. Perhaps someone needs to know the median amplitude and phase
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[robbibt]

This definitely something I would like to do - I have been doing some early experimentation with it relating to #22. The tricky thing is that not all models provide the same constituents, but I think we could still make it work by returning NaN for constituents that aren't included in some of the models.

Will let you know if I make progress on this, thanks for the feature suggestion - much appreciated!